How to use a Public IP on LAN

We cannot disable NAT on Vigor Router, but still, we may can use a public IP address on a host behind Vigor Router. If our ISP allocates a block public IP addresses for us, then we may use the public IP address with IP Routed Subnet or Routing Usage LAN.

(For Vigor3900, Vigor2960 and Vigor300B, please refer to the article here.)

Suppose ISP provides a public IP subnet 211.100.200.152/255.255.255.248 for us, and the gateway IP is 211.100.200.158. The public IP addresses we can use are between 211.100.200.153 to 211.100.200.157. The following shows how to set up a non-NAT subnet so that the server behind Vigor Router can use the public IP address 211.100.200.154.

 

WAN Setup

Go to WAN >> Internet Access and configure the WAN connection according to what ISP provides. (Note: If it is necessary to specify an IP address manually, remember that subnet mask for WAN interface should be larger than that of LAN interface.)

 

Now we have two methods to configure it

 

IP Routed LAN Setup

1. Go to LAN >> General Setup, click on Details Page for IP Routed Subnet.

2. Set up TCP/IP details for IP Routed Subnet.

  1. Enable IP Routed Subnet
  2. Enter the IP Address for the router. Note that this could be the same as router's WAN IP
  3. Enter the Subnet Mask according to ISP.

3. For the host behind Vigor Router to obtain the public IP address, we may either:

  • Configure a fixed IP/Subnet Mask on the host
  • Set up DHCP IP Pool, enable Use LAN Port, and connect the host to the router on the specified LAN port (which is port 1 and 2 in this example)
  • Set up DHCP IP pool, enable Use MAC Address, add the host's MAC address to the table, and connect the host to the router from any of the LAN ports.

After finishing above configurations, host with a public IP 211.100.200.154/ mask 255.255.255.248/ Gateway IP 211.100.200.153 will be able to access Internet through Vigor Router.

 

Routing Usage LAN

We may also create a LAN subnet for routing usage. Here we take LAN 2 for example.

1. Go to LAN >> VLAN,

  1. Enable VLAN Configuration
  2. Set up a VLAN for LAN2 Subnet
  3. Specify the LAN ports that belongs to LAN2 subnet (which is port 5 and 6 in this example), note that these are the ports to which the host should connect

2. Go to LAN >> General Setup, click on Details Page for LAN 2.

3. Set up TCP/IP details for LAN 2, 

  1. Enable LAN2
  2. Select For Routing Usage
  3. Enter the IP Address for the router. Note that this could be the same as router's WAN IP
  4. Enter the Subnet Mask according to ISP.

4. For DHCP Server Configuration, we may either:

  • Disable DHCP Server, and manually set a fixed IP/Subnet Mask on the host
  • Enable DHCP Server, and set up the DHCP IP pool according to IP range which the ISP provides

After finishing the above configurations, PC or Server that connects to Port 5 or Port 6 with IP settings as IP 211.100.200.154/ mask 255.255.255.252/ Gateway IP 211.100.200.153 will be able to access Internet through Vigor Router.

 

Trouble-shooting

If PC with public IP address setting cannot access Internet after above configuration, please check:

  • If the public IP address has been used by another device.
  • If the router's WAN Access Mode is "Static or Dynamic IP", make sure the subnet mask of WAN interface is larger than that of LAN interface.

If none of the above helps, please change the host's Gateway IP from Vigor Router's IP (211.100.200.153) to the IP Gateway IP (211.100.200.158), and connect the PC to the ISP Modem directly and see if it can work.

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